The Pipeline Safety Improvement Act of 2002 regulates management of gas transmission pipelines integrity. The Act, codified in 49 C.F.R. Part 192, significantly increased the complexity and cost of operating pipelines. Some stated objectives of the gas integrity management include improving pipeline safety through accelerating the integrity assessment of pipelines in high consequence areas; improving the government's role in reviewing adequacy of integrity programs and plans; and proving increased public assurance in pipeline safety. These regulations altered the integrity characteristics of new pipelines, and demanded the repair of many existing pipelines.
When repairing pipelines, it is often necessary to inhibit flow of product in the pipeline, and isolate pressure by inserting a stopping plug into the pipeline from, for example, a hot-taped fitting. Various types of the conventional plugs or pipeline stoppers exist and are widely used. When the repair work is finished, the stopper is removed and a completion plug is installed, sealing the fitting.
Some fittings, used for stopping flow, require the drilling of a hole through one pipe wall, while others require drilling through opposing walls. These openings, especially those with large diameters, might create a problem with running a pig through the pipeline. A pig is a device inserted into a pipeline that is designed to travel freely through it, driven by product flow to perform a specific task within the pipeline, e.g., remove wall debris, assess wall thickness, and/or assess wall deformation. Oftentimes, with conventional fittings in a pipeline, a pig can not pass through the fitting and may become lodged. To avoid potentially damaging the pig, or clogging the pipe with a lodged pig, the pig must be removed from the pipeline at a location short of the fitting, and then reinserted into the pipeline at a downstream position. This approach results in a significant loss of time and a potential loss of substantial profits, which are normally derived from use of the pipeline.
One existing solution to these problems is a type of a completion plug exemplified by T. D. Williamson Inc.'s Lock-O-Ring plug. This plug utilizes the original coupon of the pipeline cut to form the opening. The coupon is welded to a completion plug and, by being installed in a fitting, attempts to smooth the inside walls of the pipeline and therefore enable the pig to travel through the fitting.
There are some limitations with to this type of plug. One limitation includes the inability to use it with threaded completion plugs, because orienting the coupon inside the aperture during the installation process is not possible. Another limitation includes the inability to use the Williamson plug with pipes that have or will have holes in diametrically opposed walls.
Thus, there is a need in the art for a plug, insertable into a pipeline from a fitting that enables pigs to flow freely through the fitting, while eliminating pigging hazards. It is to such a device that the present invention is primarily directed.